There's also a significant trend in frame design towards steeper seattube angles. This shifts the center of mass forward, especially when pointed uphill which helps keep the front wheel from wandering.
Geometry matters. My 2020 35lb enduro bike with 170/160mm travel climbs at least as well than my 2002 28lb XC bike with 125/115mm travel. That's with a frontend that is almost 5 degrees slacker and probably 100mm longer reach. And flat pedals.
Been riding since 1988...bikes are absolutely better now than they've ever been.
(1) bars are significantly wider. Like 30+ cms in some cases. This focuses on skeletal alignment vs. muscular; think wide push-up position vs. narrow. Putting bar ends on these bars would make for an odd posture.
(2) bikes are way longer than they used to be with much slacker head tube angles. this allows you to keep more traction on the uphills in a seated position; standing (which was always less efficient) is not required as much.
There is an important change in the angle in your hip, so leg vs torso.
Modern MTB geometry puts you in a more upright position, and that opens the hip angle. This means for climbing you use more of your glutes and less your quadriceps. This is great, because glutes are the ultimate athletic muscle.
Of course, you have to get used to this position, which is markedly different to the road bike / track bike leaning ahead and closing your hip position.
It also gives you great front-back balance and easier control on your bike. Easier to jump (or just shift weight), and you have the wide bars for greater leverage.
Seriously, if someone has not tried a MTB with a modern geometry, they definitely should, they will be blown away by how much better it is than the old ages.
Add to this the dropper seatpost, and you have a winner!
Another thing to note is that with the introduction of the dropper post you can have geometry that is both friendly to climbing (rider seated directly above the chain-ring with full leg extension) and going downhill (rider out of seat and weight back above the rear wheel).
In my experience you actually don’t need additional traction on the front tire during ascents. You want more traction on the back tire, so leaning forward is more likely to cause slipping. Wider bars makes balancing easier and frames designed to keep the back wheel on the ground (by distributing more weight to the back tire) make it easier to climb.
Back in the days of 26" hard-tails you definitely needed weight over the front wheel to keep it on the ground - there was a fine balancing act of keeping enough weight over the front to not lose control while keeping that back wheel from spinning out.
Modern bike geometry is so so much better! (having tires 2.3+ inches wide helps with traction too!).
Yup, I needed to use a travel-adjust fork on my 26" full-suspension to get up steep inclines without looping. The 29er with today's geometry makes looping on a steep section so much less likely.
Pull on the bars in the direction of the rear tire/ground contact patch. This leads to more rear traction and makes a big difference in sketchy steep climbs.
Geometry matters. My 2020 35lb enduro bike with 170/160mm travel climbs at least as well than my 2002 28lb XC bike with 125/115mm travel. That's with a frontend that is almost 5 degrees slacker and probably 100mm longer reach. And flat pedals.
Been riding since 1988...bikes are absolutely better now than they've ever been.